Abstract:Ga0.47In0.53As and Al0.48In0.52As alloys, lattice matched to InP substrates, are typically grown under conditions (low substrate temperature and high V/III flux ratios) which limit cation surface mobilities. For the (Al,Ga)As system, the growth of material with low-defect density and good microscopic surface morphology is dependent on highly mobile cations which can reach kink sites on the growing surface. In the (Al,In,Ga)As system, other factors such as the miscibility gap in the AlInAs phase diagram and the volatility of InAs component dominate the growth condition requirements. In order to determine the role kinetic limitations play in reducing the quality of GaInAs and AlInAs under `normal' molecular beam epitaxy growth conditions, epitaxial layers were grown at extremely low substrate temperatures and high V/III ratios to examine the sensitivity of materials properties to these growth conditions